In vitro studies of degradation and bioactivity of aliphatic polyesther composites

In spite of numerous publications on the potential use of combinations of aliphatic polyester composites containing bioactive fillers for bone regeneration, little information exists on the combined in vitro mechanisms involving simultaneously diffusion for polymer degradation and bioactivity through nucleation and growth of apatite in simulated body fluid (SBF) solution. The objective of this study is to contribute to the understanding of the fundamentals in designing non-porous, solid materials for bone regeneration, from experimental data along with their engineering interpretation. Bioactivity, in terms of apatite growth, was assessed through several experimental methods such as scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray-diffraction (XRD) and changes in ion concentration. In the case of the six neat fillers evaluated, the filler shape, form and chemical structure showed significant differences in bioactivity response. Bioglass and calcium silicate fillers showed faster nucleation and growth rates in the screening experiments. Composites at 30 % by weight filler were prepared by solution and/or melt mixing. Polycaprolactone (PCL) composites containing five different fillers were evaluated. Solution processed PCL/calcium silicate (CS) samples showed faster bioactivity, as determined by apatite growth, compared to melt mixed samples. The onset time for bioactivity was different for all PCL composites. The limited bioactivity in the PCL composites over longer periods of time could be attributed to the PCL hydrophobicity leading to a slow polymer degradation rate, and also to the lack of SBF replenishment. For both polylactic acid (PLA) composites containing CS and bioglass, significant growth was observed after one week and in the case of CS was still evident after four weeks immersion. However, at prolonged time periods no further bioactivity was observed, although ion release results indicated a faster release rate that would eventually lead to a faster polymer degradation and possibly continuing bioactivity. The presence of silicate fillers enhanced the hydrolytic degradation rate of both PCL and PLA as shown from kinetic data calculations based on molecular weight measurements. Unfilled PLA samples showed significant embrittlement after two weeks immersion, whereas for the CS filled system more significant changes could be observed in the compressive strength and modulus after the same time period. Experimental data were also fitted into an equation proposed to calculate erosion number; in the case of unfilled PLA predictions were found to agree with literature results suggesting bulk erosion. By assuming impermeable, randomly dispersed glass flakes, water transport in a composite system, prior to significant polymer degradation could be modeled. However, modeling of transport in the case of the composite consisting of a degrading polymer and a reactive decaying filler was challenging, particularly in the case of directional bioactive reinforcements, due to the occurrence of simultaneous time dependent diffusion phenomena that altered the integrity of the sample

Modification of biodegradable polyesters with inorganic fillers

In attempts to address the growing need of materials with controlled degradation characteristics and good mechanical properties for tissue engineering applications, composites based on biodegradable polymers and a potentially bioactive novel inorganic synthetic filler were produced and characterized. Composites were produced by solution mixing of a commercial polylactic acid, as well as a biodegradable thermoplastic polyester based on butylene adipate/succinate, with synthetic magnesium/aluminum carbonate minerals, known as hydrotalcites. Two types of hydrotalcites, at 30 wto/o filler level, were used: surface coated and uncoated. Composites were also melt-mixed in a twin-screw extruder for comparison. Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Melt Rheology were used to characterize the unfilled polymers and their composites. Results of long-term degradation data in vitro in a PBS solution are also presented. The polylactic acid composites showed significant differences compared to the unfilled polymers and the copolyester composites. The copolyester composites showed only slight thermal and hydrolytic short and long-term degradation. By contrast, hydrotalcites appear to promote in all cases degradation of the matrix in the polylactic acid composites. During the course of long-term degradation of the polylactic acid and its composites, Elemental Analysis for released Mg and Al ions was performed, as well as measurement of pH changes. Scanning Electron Microscopy was also used to study morphological changes of the composites. Further investigation is needed involving degradation experiments in vivo for the most promising polylactic acid/hydrotalcite composites

Correlation of arterial hypertension with non - alcoholic fatty liver

Over the past five decades the association of essential hypertension with non-alcoholic fatty liver disease is a field of study. It is assumed that essential hypertension is an independent predictor of cardiovascular risk. On the other hand, increasingly recently scientific data highlight the role of non-alcoholic fatty liver disease in the occurrence of cardiovascular disease. So a question arose on how two independent risk factors of cardiovascular disease could be associated with each other. The existence of correlation between the two factors was reinforced by the latest scientific data showing that treatment of hypertension with certain classes of drugs, particularly for angiotensin converting enzyme inhibitors or blockers of angiotensin II receptors improves steatosis.The main finding of the study is that newly diagnosed and untreated essential hypertension, as defined by the 24-hour ambulatory recording, correlated independently with non-alcoholic fatty liver disease even after adjustment for the characteristics of the study population. Furthermore, a novel finding of our study is that the levels of the 24hour daytime systolic blood pressure correlated independently with non-alcoholic fatty liver disease. Moreover, the results of our study verify earlier data revealing a correlation between the end-diastolic diameter of the left ventricle with non-alcoholic fatty liver disease.Τις τελευταίες πέντε δεκαετίες η συσχέτιση της ιδιοπαθούς αρτηριακής υπέρτασης με την μη αλκοολική λιπώδη διήθηση του ήπατος αποτελεί πεδίο μελέτης. Είναι δεδομένο ότι η αρτηριακή υπέρταση αποτελεί ανεξάρτητο προγνωστικό παράγοντα καρδιαγγειακού κινδύνου. Όμως ολοένα νεώτερα επιστημονικά δεδομένα τονίζουν τον ρόλο της μη αλκοολικής λιπώδους διήθησης του ήπατος στην εμφάνιση καρδιαγγειακής νόσου. Έτσι, δημιουργήθηκε το ερώτημα κατά πόσο δύο ανεξάρτητοι παράγοντες καρδιαγγειακού κινδύνου θα μπορούσαν να συσχετίζονται μεταξύ τους. Η ύπαρξη συσχέτισης μεταξύ των δύο παραγόντων ενισχύθηκε από τα τελευταία επιστημονικά δεδομένα που δείχνουν ότι η θεραπεία της αρτηριακής υπέρτασης με συγκεκριμένες κατηγορίες φαρμάκων, ειδικότερα με τους αναστολείς του μετατρεπτικού ενζύμου της αγγειοτενσίνης ή με τους αποκλειστές των υποδοχέων της αγγειοτενσίνης ΙΙ, βελτιώνει την στεάτωση. Το κύριο εύρημα της παρούσας διδακτορικής διατριβής είναι ότι η νεοδιαγνωσθείσα και αθεράπευτη ιδιοπαθής αρτηριακή υπέρταση, όπως ορίζεται από την 24ωρη καταγραφή, συσχετίζεται ανεξάρτητα με την μη αλκοολική λιπώδη διήθηση του ήπατος. Επιπλέον, ένα νέο εύρημα της δικής μας μελέτης είναι ότι τα επίπεδα της 24ωρης πρωινής συστολικής αρτηριακής πίεσης συσχετίζονται ανεξάρτητα με την μη αλκοολική λιπώδη διήθηση του ήπατος. Ακόμη, τα αποτελέσματα της μελέτης μας επαληθεύουν προγενέστερα δεδομένα που ανέδειξαν τη συσχέτιση μεταξύ της τελοδιαστολικής διαμέτρου της αριστερής κοιλίας με την μη αλκοολική λιπώδη διήθηση του ήπατος

Untreated newly diagnosed essential hypertension is associated with nonalcoholic fatty liver disease in a population of a hypertensive center

Spyros Michopoulos,1 Vasiliki I Chouzouri,1 Efstathios D Manios,1 Eirini Grapsa,2 Zoi Antoniou,1 Christos A Papadimitriou,3 Nikolaos Zakopoulos,1 Athanasios-Meletios Dimopoulos1 1Department of Clinical Therapeutics, Medical School of Athens, Alexandra Hospital, Athens, Greece; 2Nephrology Department, Medical School of Athens, Aretaieio Hospital, Athens, Greece; 3Oncology Department, Medical School of Athens, Aretaieio Hospital, Athens, Greece Purpose: Recent studies have demonstrated that hypertension (HTN) is associated with nonalcoholic fatty liver disease (NAFLD) in treated hypertensive patients. The aim of this study was to investigate the association between newly diagnosed essential HTN and NAFLD in untreated hypertensive patients. Patients and methods: A consecutive series of 240 subjects (143 hypertensives and 97 normotensives), aged 30–80 years, without diabetes mellitus were enrolled in the study. Subjects with 24-hour systolic blood pressure (SBP) values ≥130 mmHg and/or diastolic BP values ≥80 mmHg were defined as hypertensives. NAFLD was defined as the presence of liver hyperechogenicity on ultrasound. Results: Body mass index (P=0.002) and essential HTN (P=0.016) were independently associated with NAFLD in the multivariate logistic regression model. Furthermore, the multivariate analysis revealed that morning SBP (P=0.044) was independently associated with NAFLD. Conclusion: Untreated, newly diagnosed essential HTN is independently associated with NAFLD. Ambulatory BP monitoring could be used for the diagnosis of essential HTN in patients with NAFLD. Keywords: ambulatory blood pressure, liver steatosis, hypertension, nonalcoholic fatty liver disease, body mass inde